GerusAudio 300B

The Perfect amplifier for your 300B's


C3G/300B Stereo Amplifier

This is my 12th custom built tube amplifier.  After trying many different valves for the input/driver stage, I have found the C3G in Triode mode to be the perfect match for the 300B. The C3G is a long life, high current valve that provides the right input sensitivity to drive the 300B, and using this valve only requires on coupling capacitor. The amp is dead silent thanks to the low ripple B+ and DC heaters for the C3G’s and 300B’s. There is no hum! 


Here are the specs for the 300B stereo amplifier:

Tubes Included: 2-C3G, 1-5U4G

Power: 8 Watts per channel before clipping (About 9 watts with some clipping)

Output: 8R

OPT’s: Lundahl LL1664 80mA

Frequency Response: 9Hz - 64KHz -3dB measured at 1 watt

Input Sensitivity: 1.3 Vrms for 8 Watts into 8 Ohms

Total Gain: 16dB

Hum: none

Size: 16W, 13D, 7.75H

Weight: 35 lbs.

Power Supply: 423VDC at 200mA

Valve operating voltages:

C3G: 205V, -3V, 15mA (Triode Mode)

300B: 342V, -70V, 79mA

Coupling Caps: Mundorf Supreme .22uF Silver/Oil

Power Supply: One 22uF 630V Capacitor, One 4mH inductor and one 100uf 500V  capacitor

Shipping to lower 48 states only

Estimated shipping cost $60-$90

717A-6B4G Specifications

  • Power: 3.5 watts into 8R
  • Input signal level: .6Volts for full power
  • Frequency response: -3dB,  9Hz-49KHz, measured @1Watt
  • Output Transformers: Lundhal 3K into 8R
  • Coupling Capacitor:  Mundorf Supreme Silver/Oil
  • Dimensions: 16.5W 12D 7.75H